Strontium isotopes in Redmond Creek Cave, Monticello, Kentucky
Loading...
Date
1999-06
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
The Ohio State University
Abstract
Redmond Creek Cave is located near Monticello in Wayne County of southcentral Kentucky, as shown on Plate 1. The cave cuts through the Kidder and Ste. Genevieve limestones and is overlain by the Hartselle, Bangor Limestone, Pennington, Breachitt, and Lee Formations. Strontium isotopes have been used to evaluate the sources of Sr in groundwater and to see if they changed over time. The 87Sr/86Sr ratios and Sr concentrations have been analyzed in bedrock and water samples taken from the surface, the cave, and its main insurgence and resurgence. Water from both the dry and wet seasons were analyzed. Also, different growth layers of a stalactite were analyzed to evaluate long-term variations. Significant variations are observed with 87Sr/86Sr ranging from 0.7082 to 0.7078 for limestone bedrock and from 0.71307 to 0.70837 for water. Sandstones of the Hartselle and Lee Formations have the highest 87Sr/86Sr ratios, up to 0.7337. In contrast, limestones of the Kidder and Ste. Genevieve formations have the lowest 87Sr/86Sr ratios near 0.7080; the limestone values are consistent with the seawater 87Sr/86Sr during the Mississippi when these rocks formed. All water samples are intermediate, indicating that they have mixed sources of their Sr. Some changes in these over time are apparent. Water from dripping speleothems have ratios closer to the limestone. The 87Sr/86Sr ratios in a stalactite show only minor variations. Overall, the values of 87Sr/86Sr in water and formation appear to reflect the paths of water flow and the degree to which the water interacted with bedrock of various types.